CS 110: Introduction to Programming in Java
	Kalamazoo College
	Winter 2008

Exercise 1: Dragging Files from Dragon

Many of the labs and programming assignments in this course will involve modifying existing programs provided for you on the college's Dragon server.  For example, in the first few weeks of the course you will be developing an Aquarium program.  You will be writing all of the logic that actually runs the program, but we will provide graphics code that your program will use.  The versions of the programs on Dragon will also include the necessary CodeWarrior project information for you to run the programs under CodeWarrior.

To run and modify the programs we provide on Dragon, you will first have to drag them to somewhere where you have the correct permissions, such as your ZIP disk, your computer in your dorm room, or the Temp folder on a machine in a lab.  The directions below assume that you are working in a lab.

• Click on "My Network Places" on the desktop.
• Click on "Entire Network."
• Single-click on the "entire contents" link.
• Click on Microsoft Windows Network.
• Click on Knet.
• Click on Dragon.
• Click on cls_compsci.  (This is where computer science classes have their Knet archives.)
• Click on cs110.
• Drag the appropriate folder to your ZIP disk, the Temp folder, or your computer. For this lab, drag three folders: AquariumLabSeries, JavaMBS, and JavaTemplates.

Exercise 2: Running a Program Using CodeWarrior; Constructing Objects in a Java Program

An object-oriented program is, as we learned in class, made up of a collection of classes.  Each class is stored in a separate file, where the name of the file is the name of the class with a .java extension.  Thus, a class called "Aquarium" must be in the file Aquarium.java.  We might have many classes in a program, and we might have many programs.  How do we keep track of which classes are part of which programs?

The CodeWarrior development environment uses a "Project" file to keep track of information about a program, such as which classes are part of the program, where the program's starting point is, and so on.  To run or modify a program using CodeWarrior, the first thing to do is to bring up its project.  You can find CodeWarrior project files by looking for files with a .mcp extension (for Metrowerks CodeWarrior Project).

For this part of the lab, you will run the Marine Biology Simulation program and experiment with constructing objects.  The Marine Biology Simulation program simulates fish moving in a bounded environment, such as a pond.

• Navigate to the JavaMBS folder you created on your ZIP disk, Temp folder, or computer in your dorm room.  (Make sure you do not navigate to the JavaMBS folder on Dragon, because the program will not run correctly there.)
• Double-click on the Code folder to move there. You will see a number of Java class files, such as BoundedEnv.java, as well as other files.
• Double-click on the OrigFishLE2.mcp file to bring up the initial version of the program. This will bring up the Project Window.  Alternatively, you could bring up CodeWarrior from the Start menu (Start->Programs->CodeWarrior for Windows->CodeWarrior IDE) and then do a File->Open to open the OrigFishLE2.mcp project file.  (Note: There is another project file in the Code folder that we will use later in the course.)
• In the Project Window you will see a Sources folder and a Classes folder.  The Sources folder contains the files for the classes associated with this program.  If you click on the little plus sign next to the Sources folder you will see a folder labeledCode, corresponding to the Code folder where you found this project.  Click on the little plus sign next to the Code folder and you will see a list of the same Java source files, such as BoundedEnv.java, that you saw before. You could double-click on any of those source files to view or edit them, but their contents wouldn't mean anything to us yet.  We will look at these classes later in the course, but for now, let's just run the program and see what it does, rather than how it does it.
• To run a CodeWarrior project, click on the triangular green "run" icon at the top of the Project Window.  (Alternatively, you could choose "Run" from the Project menu at the top of the screen or hit the F5 button on the keyboard.)  This will compile any classes that need to be compiled (the ones with the checkmarks next to them -- you will see the checkmarks disappear as each class is compiled).  It will then start running the program.
• In the Marine Biology Simulation window that appears, go to the File menu and choose "Create new environment..."  This will bring up a dialog box that will allow you to choose the dimensions for the bounded environment (e.g., the pond) in which the fish will swim.  You can set your own dimensions or use the 10 x 10 provided by default.  Then click on Create.
• Now you should see the empty environment on the left, with grid lines showing the cells where the fish could be.  On the right-hand side of the window you will see two drop-down menus.  The first lets you choose the type of object to add to the environment, but for now "Fish" is the only choice.  (We will see how to change this later in the quarter.)  The second menu lets you choose what color you want your fish to be.  The "Random" choice will give each new fish a randomly selected color.  To actually create fish in the environment, click on the cell where you want the new fish to be created.
• Experiment with constructing a number of fish in different cells.  What happens if you try to put more than one fish in the same cell?  Try clicking five or more times in a single cell.
• Experiment with the Step and Run buttons and the speed slider.  Can you figure out what rules govern fish behavior?  We will come back to this question, and to the Marine Biology Simulation program, later in the course when we are ready to work with a relatively large program.
• Exit the Marine Biology Simulation program by choosing File -> Quit or by closing the window.  Then press Enter to make the runjava.exe console window go away.  Do not, however, leave the Project Window yet.

Exercise 3: Telling CodeWarrior Where to Start

The Sources folder in the CodeWarrior Project Window usually contains multiple classes.  Furthermore, each class usually contains information about multiple operations that objects of that class can perform.  Thus, there are many operations defined in the program.  How does CodeWarrior know which operation should be done first?  And how does it invoke any operation, when it doesn't have any objects yet to do the operations?

Let's answer the second question first.  At least one of the classes in an application must have a special operation called main.  (The definition of an operation in a class is called a method definition, so this operation is called a main method.)  A main method is not tied to any particular object, so the development environment (or whatever software is running the program) can invoke it, even though it doesn't have any objects yet.  The main method then constructs one or more objects and invokes operations on them.  They, in turn, may construct objects and invoke other methods, which is the essence of an object-oriented program.  You start a Java application by invoking a main method, which is known as the target for that program.

What if several different classes have main methods?  Each main method, or target, will start up a different program, whose behavior is defined by the objects that main method constructs and the methods it invokes. 

Now let's return to the initial question.  How does CodeWarrior know which class has the main method that should be the target for this particular program?  This is just the kind of information a CodeWarrior project keeps track of.

• At the top of the Project Window is a pull-down menu, which lists the targets connected with this project.  How many targets, or variations on the Marine Biology Simulation program, are there in the OrigFishLE2 project?  For now, stick with the "Full GUI" target.  Next to the pull-down menu is a group of icons, including the Run button you used above.  Click on the first of these icons, which looks like a document with a yellow-and-black border on its left side.  This will bring up a Target Settings Window, in which you can define various kinds of information about a target.
• We are interested in how to define which class has the main method for this target.  On the left-hand side of the Target Settings window is an outline of the settings we can define.  Look for the Java Target setting under Target.  (If the Target entry has a little plus sign next to it, click on the plus sign to see the items under Target in the outline.)
• On the right-hand side you will see a text field labeled"Main Class."  This specifies the name of the class whose main method should be invoked to start the application.  (This is the name of the class, not the name of the file, so it does not have a .java extension.)  What is the Main Class for the "Full GUI" target?
• Click on the OK button to go back to the Project Window.  (If you were to change the Main Class, or any other target setting, you would have to save or apply your changes first.)
• Choose one of the other targets from the pull-down menu in the Project Window.  What is its Main Class?  What is the Main Class for the third target?
• Close the OrigFishLE2 Project Window.  Open the AquaLabSeries.mcp project file.  (Go to the AquariumLabSeries folder, then to the StartingCode folder, where you will find the project file.)
• The Aquarium Lab Series has two targets in its pull-down menu.  They both use the same Main Class; the difference between them is that one has extra settings set for debugging purposes.  We will primarily use the Java Application Release target.  What is the Main Class for this target?
• Run the Aquarium Lab Series program.  You may wish to drag its main window off to the side of the screen so that you can read the black system console window underneath.  Follow the directions in the console window.  You will notice that the program doesn't do much yet!  You will start writing the code to run this program in the first mini-lab later this week.
• Quit out of CodeWarrior.

Exercise 4: The Edit-Compile-Run Cycle

So far you have experimented with running existing programs without modifying them.  Programming, however, consists of creating new programs and modifying existing ones.  In fact, since it is almost impossible to sit down and write a program absolutely correctly from scratch, the most common behavior in programming is to edit, compile, and test existing files, whether to fix them, enhance them, or use them as templates for new development.

• Open the TemplateApplication.mcp project file in the JavaTemplates folder.
• Take a look at the MainClassTemplate.java file by double-clicking on it in the Sources folder.
• Run the program, as you have done before. It doesn't do much, but it should work. What output did you get? Is it what you expected?
• Now let's edit and personalize the program. Double-click on the MainClassTemplate.java file. Between the "welcome" and "goodbye" statements, delete the commented-out lines of code that construct and use a ClassTemplate object. Replace these statements with a line to print out "Hello, your name". (If you closed the MainClassTemplate.java window before running the program, reopen it by double-clicking on the file from within the Project Window.) Run it again. Did you get what you expected? If not, fix it!
• Now that your program no longer uses any objects of the ClassTemplate class, you can remove it from your project.  Single-click on ClassTemplate.java in the Sources folder in the Project Window to select it, then right-click on it to bring up a menu.  Choose Delete or Clear to delete the file from the project.  CodeWarrior will bring up a dialog box asking you to confirm this decision.
• MainClassTemplate and ClassTemplate are fine names for template classes, but they are not good names for classes in an actual program.  Change the name of the MainClassTemplate class to a more descriptive name for this class.  The name should start with a capital letter, since this is the convention for class names in Java.  To change the class's name in a consistent way, you will need to:
  • Edit the file and change all occurences of MainClassTemplate to the new name (for example, public class MainClassTemplate).   Don't forget the comments at the top of the file.  CodeWarrior has a Find/Replace feature (under the Search menu) similar to that in word processing and other applications, which you may use if you want.
  • In the File menu, choose "Save As" and save the file with the name of the class followed by the .java extension.  The name must match exactly, including capitalization.  Notice that this also changes the name of the file in the Project Window.  (This is the difference between "Save As" and "Save a Copy As" — saving a copy will create a copy of the file with a new name, but it will not affect the Project Window in any way.)
  • Change the name of the main class in the project's target information.  (See Exercise 3 for details.)
• You can also give the project a more meaningful name. Make sure the Project Window is active and go up to the File menu. Choose "Save a Copy As". Then type in an appropriate name, being sure it ends with ".mcp".

You may use this procedure to create a program, using the templates in the JavaTemplates folder as a starting point, anytime you need to create a new project.

Exercise 5: Saving or Backing Up Your Program

Make sure you save your program to a floppy disk, a disk on your own computer (if it's connected to the campus network), or a campus server such as cc.kzoo.edu.  Remember to save the entire folder containing your Java source files and your project file.  If you are using a floppy disk to save your work, you should remove the object code from the project (this is an option from the Project menu) before copying to your floppy disk; otherwise the folder probably won't fit.

If you used the Temp folder, be sure to clean it out before you leave by dragging everything in it to the Recycle bin. (Be sure you have save a copy first, though!)  You have a responsibility under the Kalamazoo College Honor Code not to leave copies of your labs and programming projects on machines where other students would have access to them.

Optional Follow-up Exercises: Learning More About CodeWarrior Projects

In this course we will generally provide you with the project files you need for labs and programming projects.  You may, however, wish to learn how to create new programs and new projects, rather than always modifying existing ones.  You may also want to learn how to change project configuration information other than the target's main class.  CodeWarrior provides user manuals to help you learn more about its development environment.

• Click on "Start" in the task bar. Choose "Programs", then choose "CodeWarrior for Windows, Version 6", then choose "CodeWarrior Manuals". Click on "IDE User Guide". This tutorial gives an introduction to programming concepts, and then gives instructions on working with projects and files, including editing, compiling, and running programs.
• Skip Chapter 1 of the guide, and read the section in Chapter 2 entitled "Programming Concepts". This section will give you a general idea of what is involved in software development.
• Read the section in Chapter 2 entitled "An Introduction to the CodeWarrior IDE", up to and including "Project Debugging". This section will give you an overview of the capabilities of CodeWarrior. Don't worry if you don't understand every word in this section - just try to get a feel for things.
• Now go ahead and read through Chapters 3-5. Keep in mind that there is a lot of terminology, but the goal is to get an idea of how to make and work with projects and files.
• Next, read through the first 2 sections of Chapter 10, "Compiling and Linking". This will give an overview on how we will compile projects.

Creating A New Project and Adding Files to It.

• Open CodeWarrior from the Start menu.
• Choose "New" from the File menu. Then select "Java Stationery". Type in a meaningful name for your project. Next, choose the location where you wish to store this project. (This could be your ZIP disk or the temp folder.) Select "OK".
• Now you have options for which version to use. Click on the plus sign next to JDK 1.3 (Java Development Kit). Both JDK 1.2 and JDK 1.3 are for Java 2, but for us, there really is no advantage to using JDK 1.2. Then select "Java Application" and click "OK".
• Look at the Source group - it has a TrivialApplication.java file. You should notice that this file is short on comments. You are expected to write more! (Such as author, modification dates, assistance from, descriptions of project and methods, etc.) It may be more useful to you to use the MainClassTemplate.java and ClassTemplate files from Exercise 4 as templates.
• You can add template class files (or new text files you create from the File menu) to your project. In the Project menu, select "Add Files...". After you find and select the file to add, a window will pop up. Click "OK" to add the file to the project's targets. Another window with Project messages will pop up. Go ahead and close this window. The new file should now be saved in your project. Move it up to the Source group if necessary. (To move it up, click on it and drag it up.)
• Run the program.

When you complete the lab, you can start work on Programming Project #1 (due at the beginning of Lab 2).